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EXPERT REACTION: Drought's impact on society, ecology and agriculture

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In a special issue of Science, Aussie and international researchers tackle the scientific and social impacts of droughts; past, present and future. The researchers looked at the causes of drought, the consequences for forests and soils, how drought relates to political conditions, and options for improving drought resistance in crops.

Journal/conference: Science

Link to research (DOI): 10.1126/science.aaz5492

Organisation/s: Western Sydney University, University of Tasmania, The University of Western Australia, The Australian National University, University of Technology Sydney (UTS), Deakin University, RMIT, Monash University, CSIRO, UNSW, Murdoch University

Funder: Funding statements available on each review

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Expert Reaction

These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.

Professor Kadambot Siddique is Director of the Institute of Agriculture at The University of Western Australia (UWA)

Australia is the driest human-inhabited continent in the world. Under the climate change scenario, the availability of sufficient water for crop production is becoming a problem, and it is time to improve the water use efficiency (WUE) of crops by agronomic and genetic means.

Water-efficient genotypes can be tailored based on well-suited canopy size and orientation, leaf morphology, orientation and anatomy, and root architecture to improve WUE.

Genetic variation exists in crop plants for most of the above traits, but more research is needed to determine their relative influence on WUE under well-watered, as well as water-limited conditions.

Moreover, research is needed to demonstrate that improvements in WUE will improve yields in different environments. Agronomic management techniques to improve WUE include adjusting the planting calendar according to water availability at critical crop growth stages, controlling weeds that use considerable water, soil fertility management, mulching, inter-plant spaces in crops to control evaporation, and on-farm water management.

To save water for future generations and increase crop production by using less water, water-use efficient crop species and varieties are needed along with integrated management techniques. Economic impacts must be considered before adopting any technique to improve WUE. The major objective of any agriculture-based research should be maximum production per drop of water applied or from rainfall.

Last updated: 16 Apr 2020 4:39pm
Declared conflicts of interest:
None declared.
Dr Liz Hanna is President of the Climate & Health Alliance and an Honorary Senior Fellow at the Climate Change Institute, Australian National University (ANU)

Mastering agriculture by our early ancestors secured a food supply, improved nutrition levels and health. As more people survived to older ages, populations grew. Agriculture allowed for the development of population centres, villages, towns, and cities. All were built near water supplies thereby supplying two fundamental human needs, food and water. The rise of anthropogenic megadroughts threatens to undo millennia of human advancement. 

On the one hand, this special issue on Drought tells Australia nothing new. With the world’s most variable rainfall, Australia’s drought record, sadly, is world-leading. But this series tells us a very important message - the rising intensity and frequency of droughts is a planetary phenomenon. This drought series makes it impossible to cling to the view that 'Australia has always had droughts. This current/recent one will pass and then life will revert back to normal.' Drought intensification is a global trend with no signs of reversing, so the past is unlikely to solve Australia’s drought problems of the future. 

Our normal farming operations, normal water management operations and normal bushfire preparations will be deficient. We need to prevent the worst, mitigate now, and mitigate hard. And adapt to what is barrelling down upon us. 

Warming is now tracking at 0.24°C per decade, up from 0.18°C per decade that characterised the past half-century. So we are not even close to putting a halt on the worst of what is to come. The tragedy of global pandemics will pale in comparison to runaway global heat deaths, cities running out of water, large scale crop failure and stock deaths, raging fires, economic ruin, disease and then rampant competition and conflict.

Australia’s summer of 2020 will be classed as moderate if we do not stop climate change. 

Megan Mullen speaks a universal tongue in her paper describing how fragmented water governance exacerbates inequities. Recent mismanagement of the Murray-Darling Basin, examples of water theft and government-initiated erosion of compliance monitoring, effectively sanctions the granting of unequal rights to Australians for a fundamental human need, access to water.

Acceleration of global warming and deepening climate-induced rainfall variability across this continent make it imperative that scientific rigour, transparency and fairness are applied to national water management. Failure to do so heralds widespread water insecurity, disease outbreaks, abandonment of regions and town, and ultimately conflict. Prevention is the best and only sensible option.

Last updated: 16 Apr 2020 4:37pm
Declared conflicts of interest:
None declared.
Associate Professor Andy Leigh is Associate Dean for Teaching and Learning and a Plant Ecologist in the Faculty of Science at The University of Technology Sydney (UTS)

It’s important to remember that while we’ve seen bad droughts before, a key defining feature of the droughts we’re experiencing now is that they tend to occur in conjunction with much greater temperature extremes, both hotter and for longer.

From a physiological perspective, it is much harder for plants to withstand drought when they’re dealing with temperature stress. On top of that, indirectly, high temperatures increase the severity of drought stress by increasing evaporation from the soil, so less of the rain that does fall ends up reaching plant roots.

Even if rainfall didn’t reduce under climate change, the drought stress experienced by plants will continue to worsen. This is happening already and is why we’re now witnessing widespread death of trees that have survived droughts for tens to hundreds of years.

This new research has uncovered the potential for improving the ability of plant roots to penetrate the soil in search of water; however, the authors have been careful to state that the benefit applies under conditions of ‘moderate’ drought. Unfortunately, moderate drought stress is becoming progressively less common.

Last updated: 16 Apr 2020 4:34pm
Declared conflicts of interest:
None declared.
Professor Euan Ritchie, Wildlife Ecology and Conservation, at Deakin University

Droughts are part of a natural climatic cycle in many regions, and in Australia we are especially accustomed to them. What this new research highlights, however, is that human impacts are likely to bring about more frequent, severe and extended droughts. This is deeply concerning. We have seen rainforests burn because they became tinder dry, due to drought, and then fires, associated with a warming and drying climate, set them alight. Areas of ancient forest, and their inhabitants may now be gone, forever.
 
This research adds to the concern we have for species, ecosystems, and society. More frequent, severe, and protracted droughts will increase fire risk, put further strain on already threatened species, and severely challenge food production and water supplies. The good news is that like the problems we face with a changing climate, we know that increased investment in renewable energy and more sustainable and innovative agricultural practices can go a long way to helping combat this problem. A ray of hope from the tragic COVID-19 global pandemic is that we’ve seen the international community make large changes, and quickly, such as replacing international travel with online meeting tools. To avoid the most severe scenarios and outcomes predicted for drought, we must continue to change the way we live our lives and do business, for a more sustainable and safer future.

Last updated: 16 Apr 2020 4:33pm
Declared conflicts of interest:
None declared.
Dr Joe Fontaine is a lecturer specialising in fire science and ecology within the environmental and conservation sciences discipline at Murdoch University in Perth, Western Australia

Drought doesn’t occur in a vacuum – we are experiencing hotter droughts as the planet warms. Water requirements for plants increase exponentially with temperature so that even mild drought can kill plants. Massive die-offs of trees in southwestern Australia and elsewhere have been triggered by the combination of drought and heatwaves.

These events are becoming increasingly common and link through to bushfire. Our horror bushfire season was created and driven by drought. All of the large bushfires occurred in the worst drought-stricken forests across southeastern Australia. Drought impacts will become an even more common feature of Australian life and we will need expertise and capacity to adapt our land management to this new normal.

Last updated: 16 Apr 2020 4:32pm
Declared conflicts of interest:
None declared.
Dr Samantha Grover is a Lecturer in Environmental Science at RMIT University and is the Victorian Branch President of Soil Science Australia and a Certified Professional Soil Scientist

The COVID-19 pandemic has brought home to Australians just how interconnected we are with the rest of the world. This Special Issue on drought elegantly lays out the web of interconnecting processes linking people, planet, plants and microbes that create water shortages, and how individuals and communities then live or die in response to drought.

Local examples from Australia and our tropical neighbours feature in this global review of our current understanding of processes and responses to drought, from water policy to soil biology. Water is central to life and ideas about a global response to climate change to secure water resources will resonate with Australians, as we 'stay home to save lives'.

Last updated: 16 Apr 2020 4:32pm
Declared conflicts of interest:
None declared.
Dr Susie Ho is Associate Dean of International and Graduate Education in the Faculty of Science at Monash University

Water security and climate change affect all sectors of society as well as all parts of our physical environment. We need to advocate for solutions-based learning, where students participate in decision-making processes and experience diverse socio-economic and political cultures. This should be a fundamental part of science education to meet global socio-environmental challenges.

Last updated: 16 Apr 2020 4:31pm
Declared conflicts of interest:
None declared.
Dr John Passioura is Chief Research Scientist at the Division of Plant Industry, CSIRO

The research on 'physiology of plant responses to drought' is very naive. The authors have the ebullient enthusiasm of molecular biologists of 40 years ago. They have no idea of how agronomists and breeders manage and genetically manipulate crop plants to get better performance on farms. Thinking that by studying "cellular processes" you could increase the yield of crops in water-limited environments is akin to trying to do the same for poverty resistance in humans. The last 20 years has seen exponential growth in the number of papers that aim to make plants 'drought-resistant' by genetically modifying them with single genes, genes that have been selected in a variety of ways. During this time 2800 papers on this theme have been published and have received about 100,000 citations. Not one of these papers has yet led to the release of a novel successful cultivar.
 
‘Drought resistance’ is a nebulous term. It has no defined units and is therefore not quantifiable. However, it does have a useful statistical meaning: some genotypes perform better in water-limited environments than do others. To breeders, this means, justifiably, that they are more drought resistant. 
 
Agronomically, it is much more effective to think not of drought resistance but of resource economics, i.e. by asking how to make best use of a given, growth-limiting, water supply.

This quantitative approach enables farmers to adapt in real-time to climatic changes, as happened with much success during Australia’s millennium drought and its aftermath.

Last updated: 16 Apr 2020 4:27pm
Declared conflicts of interest:
None declared.
Professor Angela Moles is a plant ecologist at UNSW Australia

Plants grow by using the energy from the sun to combine carbon dioxide from the air with water to produce glucose (simple sugar, with oxygen as a by-product). Researchers used to think that increasing CO2 in the atmosphere would result in increased plant growth, because the plants would not need to have their stomates (closable holes in the leaves that let CO2 in and water out) open for as long to make a given amount of sugar. Experiments done under controlled conditions have supported this hypothesis, but there hasn’t been evidence that it works in natural environments. This is probably because in the real world, the benefits of increased CO2 are outweighed by the disadvantages associated with increases in temperature and drought. When it gets too hot, or too dry, plants must close their stomates and so cannot produce sugars – and because they cannot completely stop water from leaking out of their stomates, they also risk running out of water, which is fatal.
 
Brodribb et al. present modelling based on the ideas above. Their model suggests that tree mortality will increase dramatically between 2040 and 2060. Once some species begin to fail, the remaining species may be more exposed to sunlight and drying winds, accelerating species’ losses. Increased fires may compound these effects. Thus, forest ecosystems may undergo substantial species losses in response to climate change, and may even change state – for example from rainforest to savanna. Such big changes in the plant communities would have catastrophic effects on many of the animal species that rely on forests.

Last updated: 16 Apr 2020 4:26pm
Declared conflicts of interest:
None declared.
Associate Professor Iftekhar Ahmed is an expert in Construction Management/Disaster Resilience from the School of Architecture and Built Environment and Faculty of Engineering and Built Environment at the University of Newcastle

This issue of Science presents scientific perspectives on drought spanning across models for understanding the phenomenon, behaviour of vegetation, and political and social aspects of water distribution.

The underlying agreement running throughout the articles is the impact of human-induced, or ‘anthropogenic’, climate change resulting in warmer temperatures and erratic rainfall patterns contributing to drought in many parts of the world including Australia; reducing emissions of carbon dioxide (CO2) can thus conceivably reduce drought risk.

While trees are great absorbers of the CO2 emitted from human activities, limits to this is posed by the moisture-depleting warming climate, which can eventually lead to their mortality. Approaches to enhance drought resilience are also presented: Plants have a resilience threshold and are able to adapt to moderate levels of drought, and the ways they do that could possibly be a basis for developing drought-resistant crops; introduction of underground bacteria, or ‘probiotics’, could enhance drought-resilience of crops.

Going beyond these scientific possibilities is the disparity both in the application of research globally and the provision of egalitarian access to drinking water supply. Perhaps most important, as acknowledged throughout, is the uncertainty confronting scientific research posed by climate change and human behaviour in relation to it.

Last updated: 16 Apr 2020 4:26pm
Declared conflicts of interest:
None declared.

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